docs: def diff_non_uni(self, y, coords, dim, coefs):
          """The core function to take a partial derivative on a non-uniform grid"""
  
          yd = np.zeros_like(y)
  
          ndims = len(y.shape)
          multi_slice = [slice(None, None)] * ndims
          ref_multi_slice = [slice(None, None)] * ndims
  
          for i, x in enumerate(coords):
              weights = coefs[i]["coefficients"]
              offsets = coefs[i]["offsets"]
              ref_multi_slice[dim] = i
  
              for off, w in zip(offsets, weights):
                  multi_slice[dim] = i + off
                  yd[ref_multi_slice] += w * y[multi_slice]
  
          return yd